This invention relates to a fixing device of a current transformer and, more particularly, to a current transformer fixing device which is suitable for fixing a current transformer contained inside a gas-insulated switchgear container to a surrounding portion of a conductor.
Hitherto, in the case of fixing a current transformer contained inside a gas-insulated switchgear container, such a construction is employed that a cylindrical current transformer is arranged, through an insulating packing, on an outer peripheral side of a current transformer mounting cylinder arranged on an outer peripheral side of a central conductor connected to an electric power line, a cylindrical container is arranged on the outer peripheral side of the current transformer, an axial end of the current transformer mounting cylinder and an axial end of the container are connected to each other through a current transformer mounting plate, an insulating packing is inserted between the current transformer mounting plate and the current transformer, a bottom side of the current transformer is supported by the current transformer mounting plate, an annular sealing flange is mounted on the other axial end of the container, a gas path is formed by providing a gap between the an inner peripheral side of the sealing flange and the other axial end of the current transformer mounting plate, the sealing flange and the current transformer mounting plate are mounted on a cylindrical tank which is a container of the gas-insulated switchgear, current transformer fixing bolts are mounted on a fixing member mounting seat fixed to an inner peripheral side of the container, and tip ends of the current transformer fixing bolts are pressed on an upper portion of the current transformer through a current transformer presser plate and the insulating packing, thereby to restrict axial movement of the current transformer and to prevent deviation by rotation.
In the conventional current transformer fixing device, the fixing member mounting seat is provided on the inner side of the container arranged on the outer peripheral side of the current transformer, and the current transformer fixing bolts are fastened on the fixing member mounting seat, so that an accommodation space between the upper side of the current transformer and the sealing flange is restricted, whereby it is difficult to make the size of apparatus small. Further, in order to avoid interference with the fixing member mounting seat during working of accommodation of the current transformer into the container, it is necessary to make the outer diameter of the current transformer smaller than the size of an inner surface of the fixing member mounting seat, whereby a radial space of the container is also limited and it is necessary to make the diameter of the container larger when a large sized current transformer is accommodated.
Further, since the container surrounding the current transformer becomes larger than the other container in general, making the size of the container larger restricts reduction of the gas-insulated switchgear.
An object of the present invention is to provide a current transformer fixing device which is able to reduce a space for accommodating a current transformer, and a gas-insulated switchgear provided with the current transformer fixing device.
To attain the object, a current transformer fixing device according to the present invention comprises a first cylindrical body surrounding the periphery of a conductor to be connected to an electric power line; a second cylindrical body surrounding the outer peripheral side of a current transformer arranged on the outer peripheral side of the first cylindrical body and containing the current transformer; an annular mounting plate connecting an axial end of the first cylindrical body and an axial end of the second cylindrical body to each other and restricting axial movement of the current transformer; an annular flange connected to the other axial end of the second cylindrical body with a gap between the annular flange and the other axial end of the first cylindrical body; and a fastening member fastened to the annular flange in an axial direction of the conductor and restricting axial movement of the current transformer.
When the above-mentioned current transformer fixing device is constructed, the following factor or factors can be added.
(1) A first container surrounding the periphery of the conductor and connected to the annular mounting plate and containing therein an insulating gas, and a second container surrounding the periphery of the conductor, connected to the annular flange and containing therein the insulating gas are provided further.
(2) An annular presser plate is arranged between the fastening member and the current transformer.
(3) Insulating packing is arranged between the current transformer and the annular mounting plate, between the current transformer and the first cylindrical body, and between the current transformer and the annular mounting plate.
(4) An air-tight surface is formed between the second container and the annular flange by connecting them, and the fastening member is arranged a position closer to the first cylindrical body than the air-tight surface.
Further, a gas-insulated switchgear according to the present invention, which has a switch arranged in an insulating gas atmosphere for opening and closing a circuit according to signals from a current transformer, and which any of the current transformer fixing devices as mentioned above is provided as a fixing device for fixing the above-mentioned current transformer to a surrounding portion of the above-mentioned conductor.
According to the above-mentioned construction, since the fastening member is mounted on the annular flange, it is possible to make narrow the space between the current transformer and the annular flange, to reduce the accommodation space of the current transformer, to accommodate the current transformer without making the diameter of the second cylindrical body large, and to contribute to reduction of the apparatus. Further, since any member is unnecessary for fixing the fastening member to the second cylindrical body, it is possible to reduce the number of parts.